The sweet diterpene glycosides of Stevia have been characterized, and eight sweet glycosides of steviol have been identified. These glycosides accumulate in Stevia leaves where they may attain from 10 to 20% of the leaf weight. On a dry weight basis, a typical profile for the four major glycosides found in the leaves of Stevia includes 0.3% dulcoside, 0.6% rebaudioside C, 3.8% rebaudioside A and 9.1% stevioside. Other glycosides identified within Stevia include rebaudiosides B, D, and E, and dulcosides A and B. Out of the four major diterpene glycoside sweeteners present in Stevia leaves only two (stevioside and rebaudioside A) have physical and sensory properties that are well characterized. Stevioside is known to be 110 to 270 times sweeter than sucrose, rebaudioside A 150 to 320 times sweeter than sucrose, and rebaudioside C 40 to 60 times sweeter than sucrose.
Of the diterpene glycosides found in Stevia extracts, rebaudioside A is known to have the least aftertaste. This aftertaste is described by many as bitter and licorice-like, and is present in all current Stevia extracts.
Rebaudioside A has been tested in mixtures with other sweeteners, such as fructose, glucose and sucrose, at sweetness intensities equivalent to 3% (w/v-%), 5% (w/v-%) and 7% (w/v-%) sucrose to determine the presence and degree of synergism in these mixtures (Schiffmann et al., Brain Research Bulletin 38:105-120 (1995)). According to the results, rebaudioside A appears to have an additive effect in mixtures with fructose and glucose, but a synergistic effect in mixtures with sucrose at sweetness intensities equivalent to 3% (w/v-%) sucrose. At sweetness intensities equivalent to 5% (w/v-%), rebaudioside A had an additive effect in mixtures with fructose, glucose and sucrose. At sweetness intensities equivalent to 7% (w/v-%) sucrose, rebaudioside A had an additive effect with a mixture with sucrose, but a suppressive effect with mixtures with glucose and fructose. In fact, no sweetener combinations were synergistic at sweetness intensities equivalent with the 7% (w/v-%) sucrose level.
U.S. Pat. No. 4,612,942 mentions that diterpene glycosides can modify or enhance flavor characteristics, such as sweet, when the amount of diterpene glycoside added is less than the sweetness threshold level of the diterpene glycoside in the orally consumable composition. However, no consumable composition containing only rebaudioside C as a diterpene glycoside for enhancing sweet flavor is described nor how the sweetness intensity of the consumable composition plays a role in the sweetness enhancing effect of a diterpene glycoside, and especially of rebaudioside C.
A need exists for more potent sweet taste enhancers that can effectively enhance the sweet taste of a carbohydrate sweetener without exhibiting an off-taste, such as a bitter aftertaste. In particular, a need exists in the art for a method of enhancing the sweetness of consumables that are very sweet, i.e., that have a sweetness intensity equivalent to from about 5% (w/v-%) to about 12% (w/v-%) sucrose.